A light control element which varies reflectance of light by means of application of a voltage is proposed (see Japanese Patent No. 5136978). The light control element reversibly changes optical characteristics. The light control element, for example, reversibly changes into a transmission state of allowing light to be transmitted or a mirror state of allowing light to be reflected. As an adoption example of the light control element, there is an example in which the light control element is applied to a window material for buildings or vehicles. In such a window material, optical characteristics are changed depending on ambient environment, and thus cooling and heating load is reduced.
In the light control element, as one of systems of changing reflectance, there is an electrochromic system. As a light control element of the electrochromic system, there is proposed a light control element in which a transparent conductive film layer, a proton accumulation layer, an electrolyte layer, a catalyst layer, and a light control mirror layer are laminated on a glass substrate. In this reflection light control element, protons (hydrogen ions H+) move between the proton accumulation layer and the light control mirror layer, and thus the reflectance is changed. In the reflection light control element, when a voltage is applied in a predetermined direction, protons move from the proton accumulation layer to the light control mirror layer through the electrolyte layer and the catalyst layer, and thus the reflectance of the light control mirror layer is changed. When a voltage is applied in the opposite direction, protons return from the light control mirror layer to the proton accumulation layer, and thus the reflectance of the light control mirror layer returns to original reflectance.
In the light control element of the electrochromic system, the electrolyte layer which characteristics are that ion conductance is high, that is, protons can move and electron conductance is low, may be used. As materials used for such an electrolyte layer, there is tantalum oxide (Ta2O5) or zirconium oxide (ZrO2). In addition, as materials used as the catalyst layer, there is palladium (Pd) or platinum (Pt).
In production of a light control element, it is known that a light control element which does not normally operate is produced. That is, in production of a light control element, a yield ratio may be decreased in some cases.